"The kryptonite that can weaken North Korea is information from beyond its borders," Blair said in a written testimony to the Senate Armed Services Committee.

North Koreans have no idea how bad things are in their country, Blair said, because they're subject to an "unrelenting barrage of government propaganda."

North Korean citizens caught with South Korean media can be sentenced to death or sent to horrific prison camps, as control of the media and intolerance for different narratives are pillars of North Korea's government.

But Blair said the US could leverage a recent trend in North Korea: cellphones.

About one in five North Koreans own a cellphone, many of which can connect to Chinese cell towers across the Yalu River along the countries' border, he said.

"Texts to these cellphones can provide subversive truth," Blair said. "Cell towers can be extended; CDs and thumb drives can be smuggled in; radio and TV stations can be beamed there."

Blair added: "The objective is to separate the Kim family from its primary support — the secret police, the army, and the propaganda ministry."

Though outside media does get into North Korea and reaches the country's elites, the US could expand efforts to flood it with outside news. The US used a similar tactic during the Cold War in setting up Radio Free Europe and Radio Liberty to combat the Soviet Union and its state-controlled media.

"Kim Jong Un understands that as soon as society is open and North Korean people realize what they're missing, Kim's regime is unsustainable, and it's going to be overthrown," Sun said.

Sun said that in the past when South Korea flew balloons that dropped pamphlets and DVDs over North Korea, Kim's government responded militarily, sensing its frailty relative to those of prosperous liberal democracies.

Blair pointed to other totalitarian states where popular uprisings have become informed and sought to take down a media-controlling dictator, concluding his testimony by saying that "once that process starts, it is hard to stop."